Gravestones may hold secrets of how the Earth's atmosphere has changed over the centuries, and scientists are now asking for the public's help to read these stones.

Little by little, atmospheric gases dissolved in raindrops cause the marble in gravestones to erode. As such, headstones can serve as diaries of changes in atmospheric chemistry over the years due to pollution and other factors.

By gathering data from marble gravestones of different ages across the globe, scientists hope to produce a world map of the weathering rates of these stones. They are asking volunteers to take measurements using simple calipers and GPS, following a set of scientific protocols that are explained online at the Gravestone Project. They can also log data into the scientific database at the site.

Naturally, volunteers are asked to follow local regulations, laws and customs when visiting graveyards, and they may need to seek permission from land managers before collecting data from these sites. Also, graves are sacred places for many in the community, and volunteers are asked to not walk on, disturb or damage a grave or gravestone in any way.

This project is part of a new global citizen science program called EarthTrek, which is administered by The Geological Society of America in partnership with organizations across the country and around the globe. Other scientific research projects currently underway through EarthTrek involve spotting hummingbirds and investigating invasive plant species.

"Being involved in EarthTrek provides people with the opportunity to be involved in real scientific research," said EarthTrek director Gary Lewis. "The data they collect while participating in a wonderful outdoor activity may make a real difference in the way we manage our environment. And it's free to participate."

More projects are soon to be added. "We are working with scientists on new projects involving hail, natural springs, animal and plant inventories, and much more," Lewis said.